Aircraft often include one or more landing gear that comprise one or more wheels. Each wheel may have a brake that is operatively coupled to the wheel to slow the wheel, and hence the aircraft during, for example, landing or a rejected take off. Aircraft brakes are not typically engaged voluntarily during take off, as brake engagement would act to impede forward motion of the aircraft. However, in the event of brake malfunction, one or more brakes may be at least partially engaged during a take off. Such engagement may not be enough to affect the ability of the aircraft to take off, and indeed, may be undetectable to the aircraft pilot and crew. In other cases, a dragging brake may prevent an aircraft from achieving takeoff speed. A pilot may elect to reject the take off in response to a dragging brake. A concern is that partial engagement of an aircraft brake during take off tends to generate heat in the brake, as the brake absorbs energy from the rotation of the wheel and thus increases in temperature.
A brake that is at least partially engaged at a time when no braking is commanded may be referred to as a “dragging” brake. If a brake drags during take off, it is not desirable to retract the wheel into the wheel well after take off due to the excess temperature of the brake. Retraction of a hot brake may pose a fire hazard and/or the tire may become too hot and fail. Thus, there is a need to detect a dragging brake at various times, such as during takeoff.